Recently, there is disclosed a technique of visualizing moisturizer applied to a face using two near-infrared spectroscopic images captured by a near-infrared camera in order to visualize a moisture change on the face.
Non-Patent Document 1 uses an InGaAs near-infrared camera (SU320M-1.7RT, manufactured by Sensors Unlimited, Inc.) having a sensitivity of a wavelength of 900 nm to 1700 nm. The obtained two near-infrared spectroscopic images are converted to a differential extinction image to thereby visualize only the moisturizer applied to the face.
Further, a method of distinguishing a skin moisture using near-infrared is also disclosed in, for example, Patent Document 1.
The technique disclosed in Patent Document 1 includes a step of obtaining reflection intensity for a near-infrared wavelength region between 1050 nm to 1650 nm at plural points of a skin, a step of acquiring skin moisture at plural points on the skin by substituting reflection intensity of a prediction formula indicative of a relationship between the skin moisture and the near-infrared wavelength region for the reflection intensity obtained in the previous of obtaining reflection intensity, and a step of distinguishing a skin moisture distribution based on the skin moisture at the plural points of the skin. [Patent Document 1] Japanese Laid-open Patent Application Publication No. 2010-25622 [Non-Patent Document] Iwasaki Hiroaki et al., “Visualization for moisture of human face by spectroscopic imaging using two near-infrared bands”, Optics Japan 2005 Tokyo, Optical Society of Japan (Japan Society of Applied Physics), Nov. 23-25, 2005.